This invention relates to an improved device and method for plumbing a recirculating water pump into a hot water heating system.
A recirculating water pump is installed in a hot water line of a home heating system to aid in forcing hot water through the heating system. A conventional recirculating water pump has connecting flanges on both the inflow side and also the outflow side. To install a recirculating water pump, a plumber conventionally uses a threaded cast iron flange to mate with each flange on the recirculating water pump so as to connect the pump into the hot water line. The following description relates to the conventional installation of one side of the recirculating water pump. The other side of the recirculating pump is plumbed similarly.
A conventional system for plumbing a hot water recirculating pump into a hot water system is shown in FIG. 1. In this figure, a conventional hot water recirculating pump A is shown having connecting flange B. An installation flange C is shown, which is conventionally constructed of cast iron. Flange C is mounted to flange B with bolts D. The installation flange C has an internal axial bore (not shown) through which water flows, which bore has internal threads (not shown) for receiving the male threads of a conventional threaded coupler E. Opposite the threaded end of coupler E is an enlarged inside diameter portion for receiving a hot water pipe F. When installing a recirculating water pump A into a hot water system F, coupler E is threaded into installation flange C. Pipe joint compound or Teflon tape is used to fill any spaces and stop leaks along the threads. Installation flange C is then bolted to recirculating pump flange B. Hot water pipe F is then soldered to coupler E in a conventional manner.
Leaks at the threaded joint between coupler E and installation flange C have been a continuous problem in the past using this method of installation. The leaks may be caused because heat from the soldering operation may melt the pipe joint compound or Teflon tape at the male end of the copper coupler, causing a leak to occur at this threaded connection. Further, the leak may be caused because the copper coupler E is of dissimilar metal than the cast iron flange C. When coupler E is soldered into the hot water pipe, the dissimilar metals expand at different rates perhaps causing these leaks to occur.
Finally, the conventional method of installing recirculating pumps is time consuming, because of the time needed to replumb the system to correct the leaks.
What is needed, is a leak-proof joint at the flange C connecting the hot water line with the recirculating pump flange A, which joint will remain leak-proof even when copper coupler E is soldered into the hot water line F.